The present invention relates generally to vacuum cleaners, and more particularly to a sensitivity adjusting apparatus of a dust sensor for use in such a vacuum cleaner.
Known is a vacuum cleaner with a dust sensor provided in an air passage between a suction opening and a dust collecting device. When dust is included in the drawn air, the dust sensor senses the dust to indicate the presence of the dust by means of an indication lamp, for example, and to heighten the rotational speed of an electric blower for a predetermined time period. However, for adequate cleaning, the adjustment of the sensitivity of the dust sensor is required in accordance with the kind of an object to be cleaned by the vacuum cleaner. For example, when cleaning a shaggy carpet, the dust detection sensitivity is required to be lowered as compared with the sensitivity for a bare floor such as a board floor, because the dust sensor tends to detect pile of the shaggy carpet as dust. Preferably, the adjustment of the sensitivity of the dust sensor is automatically effected in accordance with the kind of floor to be cleaned by a vacuum cleaner.